TimCodes · February 17, 2017 18:38 · Feb 17, 2017
diff --git a/MergeAndCount.js b/MergeAndCount.js
@@ -0,0 +1,71 @@
+
+function MergSortEntry(arr){
+
+   // console.log(arr)
+    let tempArr = [];
+    let i = MergeSort(arr, tempArr, 0, arr.length - 1)
+    //console.log(arr)
+    return i 
+}
+function MergeSort(arr, tempArr, leftStart, rightEnd ){
+
+    let invCount = 0; 
+    if( rightEnd > leftStart ){
+
+      let mid =  parseInt( (leftStart + rightEnd) / 2 );
+      invCount   += MergeSort(arr, tempArr, leftStart, mid);
+      invCount   += MergeSort(arr, tempArr,  mid + 1, rightEnd);
+      invCount   += MergeAndCount(arr, tempArr, leftStart, mid + 1, rightEnd);
+    }
+    return invCount;
+}
+
+
+function MergeAndCount(arr, tempArr, leftIdx, midIdx, rightIdx){
+
+    let invCount    = 0;
+    let leftNewIdx  = leftIdx // idx for left sub array
+    let rightNewIdx = midIdx  // idx for right sub array
+    let tempIdx     = leftIdx  // idx for temp array
+
+    while ( ( leftNewIdx <= midIdx - 1) && ( rightNewIdx <= rightIdx ) ){
+
+        if( arr[leftNewIdx] <= arr[rightNewIdx]){
+            tempArr[tempIdx] = arr[leftNewIdx];
+            leftNewIdx++;
+        }else{
+            tempArr[tempIdx] = arr[rightNewIdx];
+            rightNewIdx++;
+            invCount +=  (midIdx  - leftNewIdx);
+           // console.log('--- invcount temp--', invCount +=  (midIdx  - leftNewIdx) )
+        }
+
+        tempIdx++; 
+    }
+
+    while( leftNewIdx <= midIdx - 1 ){
+        tempArr[tempIdx] = arr[leftNewIdx];
+        leftNewIdx++;
+        tempIdx++; 
+    }
+
+    while( rightNewIdx <= rightIdx ){
+        tempArr[tempIdx] = arr[rightNewIdx];
+        rightNewIdx++;
+        tempIdx++; 
+    }
+
+    for( var i = leftIdx; i <= rightIdx; i++){
+        arr[i] = tempArr[i];
+    }
+    return invCount;
+}
+
+
+
+
+var a = [34, 203, 3, 746, 200, 984, 198, 764, 9];
+var  b = [2,1,3,1,2]
+
+//console.log( MergSortEntry(b));
+//console.log( MergSortEntry(a));